Papustyla pulcherrima 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Gastropoda Stylommatophora Camaenidae

Scientific Name: Papustyla pulcherrima Rensch, 1931
Common Name(s):
English Manus Green Tree Snail, Emerald Green Snail, Green Tree Snail
Papuina pulcherrima (Rensch, 1931)
Taxonomic Notes: Papuina pulcherrima is used by online communities attempting to avoid detection and for this reason it is an active synonym.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2015
Date Assessed: 2014-11-27
Assessor(s): Whitmore, N., Arihafa, A., Takendu, W. & Lamaris, J.
Reviewer(s): Seddon, M.B.
The snail appears to come closest to attaining a Vulnerable classification under criterion B. While threshold standards are met for the area of occupancy (AOO) and extent of occurrence (EOO), and there is decline in habitat and the number of mature individuals (criteria B1b(i,ii,iii,v)+B2b(i,ii,iii,v)), only one of the two required subcriteria are fulfilled (i.e. continuing decline) as the snail population appears neither subject to extreme fluctuations nor severely fragmented, and there are 12-13 locations. However, forest clearance is an ongoing threat on Manus Island with proposed logging, road development and agro-forestry developments currently being tabled and promoted under different guises. Under current conditions, a classification status of Near Threatened appears most appropriate for the Manus Green Tree Snail, as the species remains widespread with its habitat largely contiguous. However, should large scale deforestation begin to take place then we would recommend reclassification to a higher status based on the degree of forest loss.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Manus Green Tree Snail is found on Manus Island and has been reported from the adjacent Los Negros Island. Villagers report it is not found on the other islands surrounding Manus, although a few unsubstantiated accounts exist. The extent of occurrence (EOO) is 1,895 km2 and the area of occupancy (AOO) is 1,658 km2.
Countries occurrence:
Papua New Guinea
Additional data:
Estimated area of occupancy (AOO) - km2:1658Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:1895
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:12-13
Lower elevation limit (metres):1
Upper elevation limit (metres):720
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The threat status of the Manus Green Tree Snail has been quantified using a Wisdom of Crowds technique which estimated the change in relative density in the over the last 15 years (1998 to 2013) from surveys of local knowledge involving 400 respondents (Whitmore in press). A clear pattern of a slow decline emerged, with lower abundance reported for low-lying areas, deforested regions and to a lesser extent areas of high human population density. It was readily apparent that the probability of an area being assigned the highest ordinal ranking (i.e. the 'plentiful' category) declined between 1998 and 2013 while the probability that an area would be assigned one of the other lower categories increased. A comparison of medians of the 'plentiful' category suggested a decline from 89% of cells in 1998 to 71% of all cells in 2013: equivalent to a c. 20% qualitative decrease over 15 years.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:The species is restricted to forest and some low intensity forest-garden habitats (such as sago). Lower abundance is reported for low-lying areas, areas with less canopy cover, and areas with higher human population density.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):5

Use and Trade [top]

Use and Trade: After its existence was popularised internationally in the 1930s demand for the shell of the Manus Green Tree Snail grew, particularly for jewellery, which resulted in large numbers of shells being exported and eventually serious concerns being held over its possible extinction. This resulted in the snail being the first invertebrate to be listed on the Endangered Species Act of the United States of America. International trade has been controlled by export permit since 1975 under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) appendix II.

Despite international trade being regulated, the snail still faces potential overexploitation from legal domestic trade. Market sales data collected from the Lorengau market, over a six day period suggest that annual sales at the market may approach 5,000 shells. Investigations by the Wildlife Conservation Society (WCS) reveal that large quantities of shells are still being attempted to be exported out  of the country. Online searches revealed the sale of the shells, often marketed as antiques, occurring in open forums and internet market places based in New Zealand, Australia, and the United States of America (USA). The majority of listings avoided using the standard common name or its variant instead using simply 'land snail' and the antiquated scientific pseudonym Papuina pulcherrima rather than Papustyla pulcherrima. It is possible the avoidance of conventional nomenclature is an attempt to avoid detection by authorities. In some cases, sellers on internet market places were based in CITES signatory countries (including: Australia, Italy, New Zealand, Singapore and USA) while others were not (e.g. Taiwan). Currently, volumes of shells on sale in such online market places appear low, suggesting that the existing controls on international trade maybe adequate. However, given that the online prices of shells were often orders of magnitude greater than market prices on Manus Island, vigilance will be required to insure that illegal international demand does not fuel a resurgence in snail collection.

Threats [top]

Major Threat(s): The Manus Green Tree Snail is mostly threatened by habitat destruction through forest clearance: logging, plantation development (especially rubber) and to a lesser extent road developments. Increasing human population growth and an increasing cultural demand for deriving cash incomes from the land will likely see the rate of forest degradation increase in the future.

Harvest occurs when trees are felled as part of traditional shifting cultivation and the snails, typically found in the canopy, suddenly become exposed. Such harvesting is not uncommon but it is likely to be of lower significance than the longer term habitat degradation caused by such agricultural practices.

While harvest for illicit international trade is occurring, the volumes are not thought to be large compared to historic rates, although they may approach levels seen in the legal domestic trade. However, given that the prices of shells internationally are often orders of magnitude greater than market prices on Manus Island, vigilance will be required to insure that illegal international demand does not fuel a resurgence in snail collection.

Notable deposits of gold have been found in central Manus and a mine operation will likely result in the next decade although no details of the plan have been released (as of 2014).

The forests of Manus Island were badly affected by the 1997-1998 El Niño which resulted in a prolonged drought. Should climatic change result in increased rates of similar conditions this may constitute a future threat to the snail species, however, current predictions suggest that future incidence of drought in Papua New Guinea will decrease (Australian Bureau of Metrology and CSIRO 2011).

Conservation Actions [top]

Conservation Actions: Conservation of the Manus Green Tree Snail is likely best served by focusing effort on the protection of remaining tract of primary forest which covers much of central Manus. While specific interventions for the Manus Green Tree Snail are currently unlikely to be necessary, the security of this species could be strengthened by raising public, tourist and custom agency awareness of its CITES II status and the repercussions of illegal international trade.

Citation: Whitmore, N., Arihafa, A., Takendu, W. & Lamaris, J. 2015. Papustyla pulcherrima. The IUCN Red List of Threatened Species 2015: e.T16033A69151170. . Downloaded on 22 July 2018.
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